The invention relates to digital tape drive storage devices, and in particular, to a guiding assembly in a tape drive employing a single reel for preventing damage to a tape head during loading and unloading of magnetic tape media from a tape cartridge.
Digital data is stored on tape drives utilizing a variety of designs, but in all cases, magnetic tape media is wound between a pair of tape reels as data is transferred to or from the tape media. In the art of data storage, the physical space required to store data is an important concern. To conserve space, tape drives often use a single reel tape cartridge design, which utilizes a supply reel located within the tape cartridge and a takeup reel located within the tape drive.
After the tape cartridge is inserted into the tape drive, the tape media must be loaded into the tape drive. The loading operation is representative of connecting the tape media to the takeup reel and winding the tape media to a start point or read position. Various methods have been employed to perform this operation. One such method connects the tape media to the takeup reel via a buckle between a tape cartridge leader and a takeup leader. The tape media is terminated at one end by the tape cartridge leader, which is a strong flexible plastic strip containing an ovular aperture on its distal end. The takeup leader is a similar strong flexible plastic strip attached at one end to the takeup reel. The opposing end includes a stem and tab designed to buckle with the ovular aperture on the tape cartridge leader. After the takeup leader and tape cartridge leader are buckled, they are wound through a tape path past the tape head until the beginning of the tape media is in the read position relative to the tape head. Similarly, an unloading operation represents unwinding the takeup leader and tape cartridge leader back past the tape head and unbuckling the tape cartridge leader and takeup leader so that the tape cartridge may be ejected from the tape drive.
It is a problem in the art of digital tape drives to prevent damage to the tape head during the loading and unloading of the tape media. The tape head contains an inductive electromagnetic device including magnetic pole pieces that read and write data onto the tape media surface. Some magnetic heads include a magnetic resistive (MR) read element for separately reading recorded data, with the inductive element serving to only write data. In addition, the tape head includes a smooth surface formed by precision grinding and polishing techniques within a predetermined specification.
A known guiding assembly for moving the tape path away from the tape head during the loading and unloading of the magnetic tape media is disclosed in Morris et al., (U.S. Pat. No. 6,257,514). In Morris, the guiding assembly moves a tape guide between an engaged position and a retracted position. In the engaged position, the tape guide moves the tape path away from the tape head and in the retracted position the tape head is ready for reading and writing of data. Referring to FIGS. 1-3, the major components of the guiding assembly are tape guide 30, post and gear assembly 10 and tape head housing 20. Post and gear assembly 10 in FIG. 1 comprise a threaded post 16 with gear 12 compressed onto the bottom end. Gear 12 includes an integrally formed pin 14 extending vertically upward from gear 12.
Tape head housing 20 in FIG. 2 comprises cam bar 22 and cam stop 24. As post gear assembly 10 moves vertically downward and tape head housing 20 approaches the bottom of threaded post 16, cam bar 22 contacts pin 14. As gear 12 continues to rotate, pin 14 pivots cam bar 22 horizontally outward and away from tape head housing 20. As cam bar 22 pivots outward it contacts tape guide 30 pivoting tape guide 30 away from the tape head. A problem arises as cam bar 22 pivots toward a fully extended position.
Referring to FIG. 4, initially, as pin 12 pivots cam bar 22, sufficient torque is applied to the distal end of pivoting cam bar 22 which in turn pivots tape guide 30 away from the tape head. As cam bar 22 moves toward the end of travel as illustrated in FIG. 5, the torque applied by pin 14 on pivoting cam bar 22 and thus tape guide 30 decreases. As tape guide 30 moves the tape path away from the tape head, the torque applied by cam bar 22 decreases while the force or tape tension applied in the opposite direction by the tape media in the tape path increases. The decrease in torque applied by cam bar 22 at the end of travel is due to the contact point where pin 14 engages cam bar 22. As cam bar 22 reaches the end of travel, pin 14 applies torque to cam bar 22 at a point nearest the tape head housing 20 as illustrated in FIG. 5, thus decreasing the torque applied to cam bar 22 and tape guide 30. Therefore as the force required by tape guide 30 to move and maintain the tape path away from the tape head increases, the torque applied by cam bar 22 and thus tape guide 30 decreases.
When the tape media is tightly wound between the supply reel in the tape cartridge and the takeup reel in the tape drive, the force applied by cam bar 22 and therefore tape guide 30 has been shown to fail to move the tape path a sufficient distance away from the tape head. Likewise, after the tape path as been moved away from the tape head and the tape media is pulled past the tape head, the force applied by the cam bar has been shown to fail to maintain the position of the tape guide.
For these reasons, a need exists for a guiding assembly that applies a sufficient force to move and maintain the tape path away from the tape head to prevent the takeup leader and tape cartridge leader from contacting the tape head during the loading and unloading of the tape media.
The present guiding assembly overcomes the problems outlined above and advances the art by providing a guiding assembly that increases the force applied to the tape guide as the tape path is moved further away from the tape head. Advantageously, the guiding assembly protects the tape head from the abrasive nature of the leaders as well as the build up of static charge. In addition, the guiding assembly prevents wear on the takeup leader and tape cartridge leader caused by repetitive contact with the tape head.
The present guiding assembly comprises a tape guide pivotally connected to the tape drive within the tape path. The tape guide is configured to redefine the tape media path of travel during the loading and the unloading operations. During loading of the tape media, the tape guide is pivoted away from the tape head until the takeup leader and tape cartridge leader have been pulled past the tape head and the beginning of the tape media is in the read position. The tape guide is then pivoted adjacent the tape head for reading and writing of data. During unloading the tape guide is again pivoted away from the tape head. The tape guide remains pivoted away from the tape head while the current cartridge is unloaded, and until a new cartridge is inserted and the tape media has been loaded to the read position.
A cam bar pivotally connected to the tape head housing includes a pin integrally connected and extending downward from the cam bar. As the tape head housing approaches the bottom of the threaded post and gear assembly, the pin on the cam bar engages a cam integrally formed on the surface of the gear. As the post and gear assembly continues to rotate, the pin follows the cam rotating the cam bar away from the tape head housing. The arcuate shape of the cam is configured such that as the pin follows the cam, the rotational acceleration of the cam bar is high and the torque applied by the cam bar increases with rotation. As the pin further engages the cam, the rotational acceleration of the cam bar is tapered off. Thus, as increased torque is required to drive the position of the tape guide, the cam bar applies an increased torque. As the cam bar reaches the end of travel, the tape guide is securely held in the engaged position, as the amount of force or tape tension required to drive the tape guide back to the retracted position is maximized.
By increasing the torque applied by the cam bar as the cam bar reaches the end of travel increases the force exerted by the tape guide to move the tape path away from the tape head, thus preventing failure due to insufficient force to drive the tape guide to the engaged position. Additionally, once the cam bar has reached the end of travel, a stop at the end of the cam ensures that the cam bar and thus the tape guide consistently stop at the same position and that the tape guide is held securely in the engaged position.